/*
 * Copyright (c) Massachusetts Institute of Technology, 2007 
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *    Original code:  http://simile.mit.edu/repository/tracer/trunk/
 */

package com.google.util.logging;

import java.nio.charset.Charset;
import java.time.Duration;
import java.time.Instant;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;

import org.apache.commons.lang3.exception.ExceptionUtils;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Node;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.layout.AbstractStringLayout;

/**
 * This is a special Log4j log formatter that is capable of reacting on special log messages and 'indent' the logs
 * accordingly. This is very useful to visually inspect a debug log and see what calls what. An example of logs are
 * "> method()" and "< method()" where > and < are used to indicate respectively "entering" and "exiting".
 */
@Plugin(name = "IndentingLayout", elementType = Layout.ELEMENT_TYPE, category = Node.CATEGORY, printObject = true)
public class IndentingLayout extends AbstractStringLayout {

    protected IndentingLayout(Charset charset) {
        super(charset);
    }

    @PluginFactory
    public static IndentingLayout createLayout(@PluginAttribute(value = "charset", defaultString = "UTF-8") Charset charset) {
        return new IndentingLayout(charset);
    }

    protected static final int CONTEXT_SIZE = 25;
    protected static final long MAX_DELTA_MILLIS = 10000;

    private static final String TIME_FORMAT = "hh:mm:ss.SSS";
    private static final DateTimeFormatter TIME_FORMATTER = DateTimeFormatter.ofPattern(TIME_FORMAT)
            .withZone(ZoneId.systemDefault());
    protected Instant previousTime = null;
    protected int indentation = 0;

    @Override
    public String toSerializable(LogEvent event) {
        String message = event.getMessage().getFormattedMessage();
        if (message == null) {
            return "";
        }
        if (message.length() < 2) {
            return message;
        }

        char leader = message.charAt(0);
        char secondLeader = message.charAt(1);
        if ((leader == '<') && (secondLeader == ' ') && (this.indentation > 0)) {
            this.indentation--;
        }

        // Reset buf
        StringBuilder buf = new StringBuilder(256);

        // Event time is a log4j Instant, not Java instant, so convert it
        org.apache.logging.log4j.core.time.Instant then = event.getInstant();
        Instant now = Instant.ofEpochSecond(then.getEpochSecond(), then.getNanoOfSecond());
        Duration delta = Duration.ZERO;
        if (previousTime != null) {
            delta = Duration.between(previousTime, now);
        }
        previousTime = now;

//        if ((previousTime == null) || (delta.toMillis() > MAX_DELTA_MILLIS)) {
//            buf.append('\n');
//            indentation = 0; // reset indentation after a while, as we might have runaway/unmatched log entries
//        }

        buf.append(TIME_FORMATTER.format(now));

        buf.append(" [");
        String context = event.getLoggerName();
        if (context == null) {
            context = "<unknown logger>";
        }
        if (context.length() < CONTEXT_SIZE) {
            pad(buf, CONTEXT_SIZE - context.length(), ' ');
            buf.append(context);
        } else {
            buf.append("..");
            buf.append(context.substring(context.length() - CONTEXT_SIZE + 2));
        }
        buf.append("] ");

        pad(buf, indentation, ' ');

        buf.append(message);

        buf.append(" (");
        buf.append(delta.toMillis());
        buf.append("ms)\n");

        if ((leader == '>') && (secondLeader == ' ')) {
            indentation++;
        }

        if (event.getThrown() != null) {
            buf.append(ExceptionUtils.getStackTrace(event.getThrown()));
        }

        return buf.toString();
    }

    private void pad(StringBuilder buffer, int pads, char padchar) {
        for (int i = 0; i < pads; i++) {
            buffer.append(padchar);
        }
    }

}